Glass laminates are commonly used wherever so-called safety glass is of advantage, e.g. in automotive vehicle windows and the like where shattering of the glass may be a problem because it can endanger the occupants of the vehicle.
For this reason it has become common practice in the safety-glass art to laminate an outer glass pane to an inner glass pane with at least one layer of a bonding synthetic resin material.
The glass laminate can have a simple or complex perimetral edge in which the edge surfaces of the two glass panes and of the bonding layer are incorporated.
The term "edge" is here used to refer to the planar, rounded or beveled surfaces which run along the boundaries of each of the glass panes generally transverse to the broad surfaces thereof. The term "edge" when used without reference to the edge surfaces will then be reserved for the junction between the aforementioned edge surface and the broad base of the glass pane and is represented in cross section by a corner.
The perimetral edge will thus then be the simple or complex structure formed along the boundary of the glass laminate by the two edge surfaces of the glass pane and the edge surface of the bonding layer or layers. A simple perimetral edge can be one which is planar and in which the edge surfaces of the glass panes and the bonding layer are level with one another. A complex perimetral edge will generally be one in which the edge surface of one glass pane is set back from the edge surface of the other, in which the edge surface of the bonding layer is set back from one or both of the edge surfaces of the glass panes and in which the edge of the glass laminate can thus have a groove and/or can be stepped.
The reference of an optically-effective coating will generally refer to a metallic or metal oxide coating which can be applied to one or both of the glass panes to the bonding layer or on a foil which is sandwiched between the glass panes and thus is integrated with the bonding layer.
The synthetic resins which can be used for the bonding layer are generally known and include polyvinylbutyral or ethylenevinylacetate and polyurethanes. The glass laminates which are fabricated can be used in construction and in the motor vehicle industries, as noted, wherever safety glass is required.
The glass laminates which have been described have lives which can be measured in decades although they are subject to various influences which restrict the useful life. These can include static or dynamic mechanical stresses, thermal stresses which are often superimposed upon mechanical stresses, for example from exposure to sunlight and the like.
It is important that the laminate be formed in such manner that corrosive action, delamination and loosening of the bond between the glass panes is avoided as much as possible and for that moisture penetration into the perimetral edge of the glass laminate should be prevented. The term "corrosion" is used here in its most general sense and includes all deteriorating influence, including moisture penetration, damage to functional layers such as to an infrared reflecting silver layer, etc.
In order to reduce the effect on the laminate of such influences, it is common to completely or partially seal the perimetral edge and thereby maintain the long useful life of the glass laminate.
EP 0 391 165 A3 describes the sealing of the edge of a glass laminate of automotive vehicle window glass by means of a synthetic resin of the fluoropolymer, polybutenepolymer or butylpolymer type applied to a planar or simple perimetral edge of the glass laminate. The sealing of the perimetral edge has not, however, been fully satisfactory. For some time it has been known to provide the perimetral edge with a groove (UK Patent 310 065) which widens outwardly and receives a plastic seal not described in detail in this reference.
In neither case has the application of plastics by prior methods to the perimetral edge been fully satisfactory. In the past, the plastic has been doctored onto the perimetral edge in the form of a paste by a blade or the like. This method is not compatible with serial production techniques and it is difficult to obtain a completely uniform sealed edge.
The sealing layer is not, moreover, a structure layer which is capable of imparting strength to the glass laminate. It furthermore does not have a naturally-occurring contour or configuration or surface so that the nature of the seal will depend largely on the manipulative steps with which it is applied.